Triturating and mixing machine



Nov. 20, 1956 TRITURATING AND MIXING MACHINE Filed July 15; 1954 gm, IT

M. ANDIS 2,771,280

4 Sheets-Sheet 1 INVENTOR.

Mn THE W Halal 5 aii-q', AM, m

Nov. 20, 1956 M. ANDIS 2,771,280

TRITURATING AND MIXING MACHINE Filed July 15, 1954 4 Sheets-Sheet 3INVENTOR.

MA THE-"W Awe/3 Nov. 20, 1956 M. ANDIS 2,771,280

' TRITURATING AND MIXING momma Filed July 15; 1954 4 sheeis sheet 4 '44\1 JNVENTOR.

MA HEW fl/vo/s Arraeuew/S United States Patent 2,771,280 TRITURATING ANDh/IIXING MACHINE Mathew Andis, Racine, Wis., assiguor to Andis ClipperCo., Racine, Wis, a corporation of Wisconsin Application July 15, 1954,Serial No. 443,569

19 Claims. (11. 259-408) This invention relates to a triturating andmixing machine. The device herein disclosed is an improvement on thedevice of Patent 2,020,450 in the following principal respects.

The mixing fingers comprise laterally spaced prongs which are entirelyfree of each other and unconnected by any cross bar for their entirelength of immersion. This makes it much easier to force the prongs intothe material to be acted on thereby. The cross bar has heretofore beenrequired to prevent operation of the machine in the event that the mixerstraddles the rim of the cup. In the present device, the cup has a depthagain as great as its capacity requires. There is a correspondinglyincreased range of cup movement. Hence, it is unnecessary to provide anybridge between the prongs of the triturating head.

The cup or container for the material to be triturated is shouldered tocooperate with a closure which is carried by a sleeve which isstationary during normal operation but which is free to rotate followingnormal use for the purpose of discharging from the closure and thetriturating head all food tending to adhere thereto. A clutch betweenthe closure and the driving spindle is disengaged during normaloperation and re-engaged when the closure is relieved from pressureagainst the shoulder of the container.

The spindle which carries the triturating head is belt driven and thedriving motor is bodily movable to and from driving position, beingretracted from such position while the motor is started and beingengaged with the belt only when it is desired that the head be operated.A brake is provided for the spindle and serves not only to stop thespindle immediately at the conclusion of the triturating operation, butalso to assure that the belt will be free of the driving motor pulley,rather than free of the spindle pulley, in the retracted position of themotor. Lateral confining means is provided along the path of the belt toengage the belt only when the belt is slack and to assure theaccumulation of the slack about the driving motor pulley.

A control lever having four positions is provided. From its neutralposition, the lever is movable forwardly to lift the. container aboutthe triturating head and to close the motor switch. In a further forwardposition, the lever holds the switch closed and engages the drivingmotor pulley with the belt to rotate the head, while raising thecontainer into engagement with its closure and disengaging the closureclutch from the spindle.

Returning the control handle back to its neutral position arrests themovement of the spindle, re-engages the closure therewith, lowers thecup to a level in which the closure is still within the cup but adjacentits rim, disengages the driving pulley from the belt, and finally opensthe motor switch. Continued rearward movement of the control handle toits fourth position re-engages the driving pulley with the belt,releases the brake and closes the motor circuit to rotate thetriturating head and closure within the container for centrifugalcleaning purposes.

In the drawings:

Fig. l is a view in perspective showing the device of the presentinvention as it appears when the cup or con tainer is not mountedthereon.

Fig. 2 is a view in side elevation, with portions broken away, showingthe cup elevated to engage it with the closure and illustrating indotted lines the other three positions of the control handle.

Fig. 3 is a view similar to Fig. 2 showing the position in which thehandle is arrested in the event that the triturating head straddles therim of the cup.

Fig. 4 is a detailed view of the device in axial section on an enlargedscale.

Fig. 5 is a plan view of the device as it appears with the coverremoved.

Fig. 6 is an inverted plan view of the device.

Fig. 7 is a detailed view taken in section on line 7--7 of Fig. 4.

Fig. 8 is a fragmentary view similar to Fig. 4 showing the parts in adiiferent position.

Fig. 9 is a detailed view showing the switch in elevation and taken inthe plane indicated at 9-9 in Fig. 4.

The machine housing generically designated by reference character 10comprises a lower section 11 having a base 12 and an upper section 13having an overhanging arm 14 and a cover 15.

The support for the container 16 is essentially similar to that shown inthe prior patent above identified. It comprises a verticallyreciprocable slide 17 for which the housing 10 provides a guide at 18.The slide has a seat at 19 upon which the bottom of container 16 isreceivable and it has a strap 20 which engages the bottom of thereceptacle to arrest further upward movement of the slide in the eventthe receptacle is not properly positioned (see Fig. 3).

The triturating head 21 comprises a pair of prongs 22, 23 which arewidely spaced and have no connection with each other except throughtheir common mounting at the end of the drive spindle 25. The cup orcontainer 16 is of such dimensions as to receive substantially itsentire contents within its lower portion 26 below the annular shoulder27 which is approximately midway of the height of the container. Adeeply indented rib may be provided at 28 to restrain the contents ofthe cup from rotating with the triturating prongs 21 whereby tofacilitate the movement of the prongs relative to the contents toexpedite the triturating action. When the cup is properly positioned asshown in Fig. 4 (before being lifted to triturating position), thetriturating head 21 will be within the upper portion 29 of the cup,above the shoulder 27 thereof.

The flanged bearing sleeve 30 surrounding spindle 25 is bolted to theunder surface of the overhanging housing arm 14. A counter-bore providesa seat for the outer race of bearing 31. The lower end of the shaft isguided by the bushing 32 from the lower end of sleeve 30.

Rotatably mounted externally of bearing sleeve 30 is the tubular support34 for closure 35. The closure is sufficiently large to seat on shoulder27 in the elevated position of container 16. The entire closure and itssupport are yieldable axially in a vertical upward direction on bearingsleeve 30 in response to upward thrust of cup 16 against the closure. Anannular plastic seal provided at 36 between the upper end of the tubularsupport 34 and the flange of the bearing sleeve 30 is suffi cientlyflexible to accommodate the slight degree of axial movement required.

Within the tubular support 34 is an annular clutch housing 37 which alsoserves as a seat for compression spring 38. The clutch element 39 whichhas a pressed fit in housing 37 is thereby made fast to the tubularsupport34 and closure 35.

Complementary to the female clutch element 39 is a male clutch element40 mounted on the reduced end of spindle to rotate therewith. When theclutch elements are-engaged, spindle rotation will be transmitted toclosure and its tubular support 34. However, when the closure 35 and itssupport 34 are moved upwardly by engagement of receptacle shoulder 27with the closure, the driven female clutch member 39 is moved'againstthe compression of spring 38 free of the driving male clutch element 40,thereby disengaging the drive to the closure and permitting the. closureto remain stationary during spindle rotation.

An annular plate 41 held by the screws which anchor the clutch housingannulus 37 has an internal groove for the annular seal 42 which protectsthe clutch from the material acted upon-by the triturating head. Theseal 42 may desirably take the form of an O-ring of synthetic rubber.

Within the housing extension 14, the spindle carries a driven pulley 45actuated by a V-belt 46 from a driving pulley 47 mounted on the armatureshaft 48 of motor 50. The motor is supported in a nearly uprightposition on strap metal arms 51 which are sufficiently resilient so thatthe motor is normally biased toward the position in which it isillustrated in Fig. 4, the motor being bodily yieldable from theposition of Fig. 4 to the position of Fig. 8 to engage pulley 47 withV-belt 46 to drive the spindle 25. The disclosed arrangement functionslike a clutch which normally maintains the driving pulley 47 disengagedfrom the V-belt.

The V-belt tends to remain in the Fig. 4 position with all of its slackaround the driving pulley 47. This is due in part to the functioning ofthe brake which acts on the driven pulley and it is due in part to theresiliently yieldable belt-confining guides 52 which are immediatelyadjacent both of the runs of the belt between the two pulleys, as shownin Fig. 5. When the belt is under tension, there is no substantialcontact between it and the guides. When the tension is released, theguides prevent the belt from expanding laterally, thus maintaining itsslack accumulated at the driving end.

Mounted on the motor casing is a yoke'54'from which an arm55 extendsupwardly to support the brake 56. Thebrake lining 57 (Figs. 4and 5) isnormally engaged withthe rim of pulley 45 when the motor is in theposition toward which it is biased by its resilient supporting straps51. When any triturating operation is being completed, the initialmovement of the control handle toward its neutral position allows themotor to move to the position of Figs. 4 and 5, thereby simultaneouslydisengaging the driving pulley 47 from the V-belt and engaging the brakewith the driven pulley. The abrupt deceleration of the driven pulleytends to hold the V-belttightly in the groove thereof, thereby assuringthat all the slack of the V-belt is accumulated around the drivingpulley.

The control handle 60 is connected with rock shaft 61 (Figs. 4, 7 and8). The vertical position in which it -is shown in dotted lines in Fig.2 and in full lines in Fig. l is its neutral position. Within thehousing, the rock shaft 61 has fixed to it a set of four cam levers 62,63,164 and 65, as best shownin Fig. 6. Rotatably carried betweensuccessive pairs of levers are the cam rollers 66, 67, 68 and 69. Therollers 66 and 69 operate simultaneously upon the respective camfollower arms 70 and 71 which engage the actuating posts 72 of the cupsupporting slide 17 for operation thereof in much the manner of theformer patent above identified. When the handle 60 is moved from theposition of Fig. l to that of Fig. 2, the rollers 66 and 69 engage thecam follower surfaces 73 (Fig. 4) to oscillate the arms 70 and 71 up:wardly to lift the container support. The arcuatesurface'shown at'74 inFig. 4 is, in the elevated position of the arms, concentric with rockshaft 61 to provide for a dwell to hold the receptacle in its elevatedposition against closure 35 during continued oscillation of rock shaft61 to engage the drive to the spindle.

The motor switch and the spindle drive may be actuated in eitherdirection of oscillation of rock shaft 61. When the lever 60 is moved tothe solid line position of Fig. 2, the extension 75 of lever 64 willengage the oscillatory carrier 76 of the mercury switch 77 to move suchcarrier from its normally tilted position to the horizontal positionshown in dotted lines in Fig. 9, thereby closing the circuit to motor50. The lever ex tension 75 presents a broad surface to the arm 78 ofthe carrier to hold the switch closed during continued lever movementtoward the position of Fig. 8.

If the control lever 60 is moved clockwise toward the position shown indotted lines at the right in Fig. 2, the extension 80 of lever 63engages the arm 81 of carriage 76 at the other side of the fulcrum 82 ofthe carriage, whereby the carriage is likewise moved to a horizontalposition in which switch 77 is closed. This position of the parts isused to clean the triturating head and the closure 35 in a manner whichwill hereafter be explained.

The drive to the spindle is likewise closed in each direction ofoscillation of rock shaft 61 from its neutral position. If the lever 60is moved counterclockwise to the dotted line position shown at theextreme left in Fig. 2, the cam roller 67 engages the cam follower 83,as shown in Fig. 8 to lift the follower in the guideway provided at'84inthe housing. An adjustable stop at 85 engages an integral portion of thehousing to limit the upward movement of the follower. The followercarries the arm 86 of a slide 87 guided at the rear of the housing andcarrying at its upper end a cam 88 adjust ably connected to bar 87. Theadjustment is conveniently made by providing the cam and the bar withmating teeth and using screw 89 to hold the cam to the bar in anydesired position of adjustment.

As the cam advances upwardly to the position of Fig. 8, it engagesroller 90 which is carried between duplex levers 91, 92, as best shownin Fig. 5. The levers 91, 92 are notched at 93 to engage a pin carriedby the yoke 54 which is connected to the motor shell, as best shown inFig. 4. The movement thus developed oscillates the lever 91, 92 from theposition of Fig. 4 to the position of Fig. 8, thereby oscillating themotor 50 on its resilient supports 51 to engage driving pulley 47 withthe belt 46 in the manner already explained.

In the clockwise oscillation of lever 60 from its neutral position ofFig. l to the dotted line position shown at the right in Fig. 2, theroller 68 is engaged with cam follower arm 83 to effect a like upwardmovement of bar 87, resulting in a like engagement of the driving pulley47' with the V-belt 46. This upward movement is opposed, in both cases,by compression spring 95 (Figs. 4 and 8).

Operation of thedevice is as follows:

The material to be acted upon by the triturating or mixing head isplaced in the receptacle 16 to a depth which does not normally exceedthe level of shoulder 27. The-cup is thereupon moved into position onthe support 19, as shown in Fig. 4. The prongs 22, 23 of the trituratinghead 21 will be entirely above the level of the contents of the cup atthis point.

The arm 60 is now-moved forward from its neutral positionto the positionshown in full lines in Fig. 2. This raises the container to such a levelthat the shoulder 27 engages closure 35 and slightly lifts the closureon the spindle to disengage the female driven clutch element 39 from themaledriving clutch element 40 on spindle 25. Substantially concurrentlythe mercury switch is tilted to close the motor circuit but spindlerotation is not yet initiated. It is desired to note the fact that manyof the materials acted upon in a machine of this kind are extremelysolid, ranging from hard frozen ice cream to'fruits, some of which mightbe quite green. In the past, it has been extremely difficult to forcetriturating prongs into more or less solid materials because of thetransverse Connecting bar heretofore provided in all such devices as asafety measure. The construction herein disclosed eliminates such a barand thereby makes it quite easy to force the prongs into the work. Thebar is made unnecessary because of the substantial depth of the cup andthe arrangement whereby any misplacement of the cup in the manner shownin Fig. 3 will result in interference by the cup with the free upwardmovement of the stirrup strap 20 on slide 17, thus making it impossiblefor the control lever 60 to be moved to the point of closing the switch.

Assuming that the switch is closed in the proper use of the apparatus aspreviously described, continued counterclockwise movement of the controllever 60 from the position of Fig. 2 will hold the switch closed butwill transmit motion from the roller 67 to the cam follower arm 83 totilt the motor 50 to the right from its Fig. 4 position to its Fig. 8position, thereby causing the rotation of the armature shaft to becommunicated to the spindle. In practice the spindle is immediately setinto operation at approximately 3400 R. P. M. Gnly a matter of a fewseconds is required to complete the mixing or triturating operation.Three to five seconds is normally adequate. Despite the extremeagitation within the container, the contents are confined by the closure35.

The operator will almost immediately return the control lever 60 towardits vertical neutral position. The very first movement of the leverapplies to break the spindle and disconnects the drive by permitting themotor to be returned to the position of Fig. 4. During the downwardmovement of the work receptacle incident to this initial movement of thecontrol lever, the closure 35 moves with it to re-engage the cone clutchwhich normally connects it with the spindle. Thus, before the closureleaves the receptacles shoulder 27 upon which it is seated in use, themotor drive has been disconnected from the spindle.

In the extreme position of the carrier 17, 19 for the container 16, theclosure 35 is still within the mouth of the container. Accordingly, ifthe operator desires, he may clean the closure and the triturating headcentrifugal- 1y by simply continuing the clockwise oscillation ofcontrol lever 60 to the position shown in dotted lines at the extremeright in Fig. 2, thereby re-closing the motor switch and re-engaging thedrive to the spindle as already described. This time the closure 35 isclutched to the spindle to rotate therewith to centrifugally dischargeinto the upper end of the container any material which may haveaccumulated upon it. Yet the fit of the closure to the container is suchthat there is little or no possibility that any of the centrifugallydischarged material thrown off of the triturating head or the closurewill escape from the container.

I claim:

1. In a mixing device using a pronged mixing head for trituratingmaterial in a cup, the combination of a cup support and mixing head andmeans mounting said support and head for relative axial movement, themixing head comprising prongs having free portions at leastsubstantially equal in length to the full depth of immersion in thecontents of the cup, the space between said prong portions being openand unobstructed and the cup having a bottom portion adapted to receivecontents for trituration by said prongs and having an upward extensionbeyond said bottom portion substantially equal in extent to the depth ofsaid bottom portion, the mixing head having means at a level above theopen and unobstructed space between the prongs to engage the cupextension before the prongs substantially penetrate the contents of thebottom portion of the cup in the event of relative lateral displacementbetween the mixing head and cup, said cup support having support meansspaced from the cup engaging means on the mixing head a distance greaterthan the height of the cup, the mixing head being bodily receivable intothe cup to engage said prong portions substantially full depth in thecontents of the cup in the event the cup and mixing head are properlyaligned, and means for effecting relative movement between the cupsupport and mixing head in an axial direction for a distance sufficientto cause the free end portions of the prongs to traverse the wholelength of the extension and to penetrate to substantially full depth thecontents in the bottom portion of the cup, together with means foreffecting relative rotation between the mixing head and cup and having acontrolling switch actuated by the means for effecting relative axialmovement between the cup support and mixing head as prongs approachsubstantially full immersion in the contents of the cup, whereby saidswitch will be inactive if said extension engages the mixing head in adisplaced relative position of the cup to block axial movement of saidcup support.

2. In a device of the character described, the combination with arotatably mounted mixing head comprising a spindle and prongs havingfree and unobstructed workengaging portions extending laterally anddownwardly from said spindle, switch controlled spindle rotating means,a cup having substantially twice the depth of the prongs and into whichthe mixing head is bodily receivable when properly aligned with the cup,said cup having a work-receiving portion constituting substantially halfof its total height, an elevating platform for the cup, means foractuating the platform through a length of travel sufficient to effectmovement of said prongs through the upper portion of the cup intocontents confined substantially exclusively to the lower portionthereof, and means on said mixing head spaced from said platform adistance greater than the height of the cup and against which the upperportion of the cup is engaged under pressure of the platform if said cupis misaligned with the mixing head whereby to preclude elevation of theplatform, said platform actuating means including means for operatingthe switch to initiate movement of the mixing head only when saidplatform is substantially completely elevated and said prongs aresubtsantially fully engaged in the cup.

3. In a device of the character described, the combination with aspindle carrying a mixing head of a cup closure mounted on the spindleand rotatable with respect thereto, clutch means for releasablyconnecting the closure to rotate With the spindle, said clutch meansbeing releasable upon axial displacement of the closure from the mixinghead and a cup adapted to receive contents to be acted on by the mixinghead and into which the mixing head is receivable, said cup having ashoulder complementary to said closure and adapted to lift the closureto effect dis-engagement of the closure clutch, and means for moving thecup to and from an operative position in which the mixing head isimmersed in the cup and the cup shoulder is engaged with said closure ina clutch releasing direction.

4. The device of claim 3 in further combination with spindle actuatingmeans and means whereby said spindle actuating means is operated whensaid closure is declutched from the spindle.

5. The device of claim 4 in further combination with means for effectingoperation of the spindle actuating means with the closure clutched tothe spindle, the cup having an upward extension within which the closureand mixing head are disposed above the level of the contents of the cupwhen the spindle actuating means functions With the closure clutched tothe spindle.

6. In a device of the character described in combination with a spindleand housing providing mounting bearings for the spindle and havingdriving connections to the top of the spindle, of a closure membermounted coaxially with the spindle, clutch means normally biased intoengagement for driving the closure from the spindle, said clutch meansincluding driving and driven clutch parts connected with the closure andspindle and disengageable upon upward axial movement of the closurerespecting the spindle, a cup elevator mounted on the housing, and

amp detachably positioned on the elevator and movable therewith upwardlyrespecting the spindle, the spindle having a mixing head adapted to bereceived into the lower portion of the cup and the cup having a shouldercomplementary to said closure and engageable with the closure in anelevated position of the cup to effect axial displacement of the closureto disengage its clutch element from that of the spindle.

7. The device of claim 6 in which the cup has an upward extension abovesaid shoulder of sutiicient height and width to receive the closure andthe mixing head when the mixing head is substantially entirely abovesaid shoulder.

8. The device of claim 7 in further combination with elevator operatingmeans comprising control means for effecting actuation of the spindle intwo positions of the cup, in one of which the shoulder is engaged withthe closure and the closure is dcclutched from the spindle, the otherposition of the cup being one in which the mixing head and closure arewithin the cup extension and substantiallyentirely above the shoulder,the closure being clutched to the spindle.

9. The device of claim :3 in which the -indle has a motor assemblyadjustably mot .itcd within the honing for movement between two 9.,ttions and comprising driving pulley bor." movable to and from thespindle, the spindle carrying a driven Finley and the pulleys beingconnected by a belt respect ly in driving and non-driving engagementwith one or the pulle according to the position of the motor assembly.

it). The device of claim 9 in which said motor assembly furthercomprises brake selectively engageable with the spindle pulley in thenon-beltdriving position of said assembly and diseugageable from thespindle pulley in the movement of said assembly in a belt engagingdirection.

11. The device of c with belt guide di and the spindle pull-e of thebelt between s2 said belt, whereby to "T the belt from the drivingpulley tpon bodily mo emcnt of said assembly in a beit disengagingdirection.

l2. A mixing de ice oi the type in which a cup is elevated about adriving raindle prov ded with a mixing head, said device compi' thecombination With such a spindle and the cup ot a cup closure having areleaseable clutch connection with the spindle, means for disengaging:the clutch connection to permit the closure to remain non-rotatable\Vlicfi the mixing head is operative Within the cup, m.-

t'or engaging tne clutch to cause the closure to re with the spindle enthe spindle is tota ed with its mixing head disengaged from the contentsof the cup, spindle actuating means, and an elevator actuator comp: 'zgtwo arate controls for rendering s spindle "stunting means effective todrive the spindle, one of sa controls comprising means for rotating thespindle with the cup closure tie-clutched therefrom and the other saidmeans comprising means for rotating the sp is with the closure clutchedthereto.

13. The device of claim 12 in which the said cup is of such height toenclose the mixing head and closure when the spindle is by both of saidin is.

14. A device of the character described comprising a housing provided onits side with a cup elevator and a bearing sleeve above the elevatorhaving a spindle rotatably mounted therein, a driven pulley carried bythe spindle at its upper end, a mixing device carried by the spindle atits lower end, cup closure mounted on the spindle and having a clutchconnection thereto disengageablc upon upward displacement of the closurerespecting the spindle, and a cup dc chably mounted on the elevator andhaving -.t lower gorticn adapted to receive material to be mixed -;lupward extension of suliicient height above the lower g' ortion toenclose the closure and mixing head while the latter is substantiallydisengaged from Q in further combination between the driving pulley ofthe path of movement 'oncd to confine such materiel, said cup having anintermediate portion complemcn iry to the closure to be substantiallysealed thereby above such material in an elevated position of the cup,motor assembly pivotally mounted within the housing and comprisingdriving shaft and pulley at the level of the driven pulley on thespindle, a V-bclt trained about said pulleys, the assembly beingpivotally movable in directions to tighten and loosen said belt, a rockshaft provided with a handle and having an elevator ng connection, cammeans actuated from said shaft scillating said assembly in a belttightening direction l JZl move 1311i of said elevator to a position inwhich said. closure is sealed to the intermediate portion of the cup, amotor control switch having means controlled by rock shaft for itsclosing operation, said switch being c-pcrativ ly connected to controlthe operation of the motor, and. r cans connected with said rock shaftfor sing said switch operate the motor and for oscillatmotor in, abelt-tightening direction in the course oi: an opposite movement of therock shaft with the elevator in lowered position in which the mixinghead and closure are within portion of the cup above its saidintermediate portion.

15. The device of claim 14 in which the motor assembly comprises a brakeshoe mounted thereon in a position of normal engagement with the drivenpulley on the spindle, said shoe being disengageable from the drivenpulley in the movement of the assembly in a belt tightening direction.

16. The device of claim 15 in further combination with means laterallyconfining the belt between the driving and driven pulleys whereby toaccumulate slack about the driving pulley in the position of theassembly in which the driving pulley is disengaged from the belt and thebrake is engaged with the driven pulley.

17. In a device of the character described, the combination with arotary mixing head having a driven pulley, a cup support, and meansincluding a control lever for moving said support axially toward themixing head, of an electric motor for rotating said head, said motorhaving a drive pulley and a belt interconnecting said pulleys, said belthaving a bight within which the drive pulley is disposed said motorhaving a mounting on which the motor is bodily shiftable between a firstposition in which the belt is tensioned against the drive pulley and asecond position in which the belt is slack with respect to said drivepulley, belt guide means laterally confining the belt to maintain saidbight in a position from which the drive pulley withdraws in the secondposition of the motor and interconnections between said control leverand said motor whereby movement of the lever in a direction to move thecup support toward the mixing head shifts the motor into its said firstposition.

18. The device of claim 17 in which the motor mount ing comprises aresilient support connected to the motor at the end thereof which isopposite its drive pulley, the end of the motor nearest said pulleybeing provided with a coupling to said interconnections whereby themotor is moved on its resilient support in response to control levermanipulation.

19. The device of claim 17 in further combination with a brake for saidmixing head, and interconnections between said brake and said motorwhereby said brake is released in the movement of the motor to its saidfirst position.

References Cited in the file of this patent UNITED STATES PATENTS1,291,728 Beach Jan. 21, 1919 1,351,243 Graves Aug. 31, 1920 2,021,626Flegel Nov. 19, 1935 2,168,429 1939 2,463,697 1949 2,589,615 1952

